Direct-positive silver halide photographic materials are used for copy of various kinds of photographs. In most cases, they are used for printing positive copies from positive original images or negative copies from negative original images. Such direct-positive photographic materials have been previously obtained by using a prefogged direct-positive silver halide photographic emulsion. In order to fog emulsions, there can be used various known methods including an optical, chemical or another treatment. Especially good results can be achieved, e.g., by using the methods described in Scientifique et Industrie Photographie, 28, January, 57-65 (1957). More specifically, silver halide grains are fogged with highly intense light, or by reductive fogging with thiourea dioxide, stannous chloride or the like, or using a gold or another noble metal compound. Also, the combination of a reducer with a gold compound or a compound of a metal which is more electrically positive than silver (e.g., a rhodium compound, a platinum compound or an iridium compound) can be used for fogging silver halide grains.
However, the direct-positive silver halide photographic materials obtained by such the methods as described above frequently cause large changes in sensitivity, D.sub.max and D.sub.min upon long-term storage, particularly under the condition of high temperature and high humidity. Accordingly, further improvement is required thereof.